Long life NA/NiCl2 cells

Abstract

The premature capacity failure of Ni/NiCl2 secondary cells due to agglomeration of nickel particles on the surface of the NiCl2 cathode is prevented by addition of a minor amount, such as 10 percent by weight of a transition metal such as Co, Fe or Mn to the cathode. The chlorides of the transition metals have lower potentials than nickel chloride and chlorinate during charge. A uniform dispersion of the transition metals in the cathodes prevents agglomeration of nickel, maintains morphology of the electrode, maintains the electrochemical area of the electrode and thus maintains capacity of the electrode. The additives do not effect sintering. The addition of sulfur to the liquid catholyte is expected to further reduce agglomeration of nickel in the cathode.

We claim: 
     
       1. An electrode for a Na/NiCl 2  secondary battery comprising NiCl 2  containing a dispersion of from 1 to 25 percent by weight of particles of a transition metal having a lower potential than nickel. 
     
     
       2. An electrode according to claim 1 in which the transition metal reversibly chlorinates under the electrochemical condition of the cell. 
     
     
       3. An electrode according to claim 2 in which the transition metal is selected from the group consisting of Co, manganese and iron. 
     
     
       4. An electrode according to claim 3 in which the transition metal is present in an amount from 5 to 15 percent by weight. 
     
     
       5. An electrode according to claim 4 in which the transition metal is present in an amount of about 10 percent by weight. 
     
     
       6. An electrode according to claim 1, in which particles of nickel, the transition metal and sodium chloride are sintered to form said electrode. 
     
     
       7. A rechargeable Na/NiCl 2  cell comprising in combination a first body of molten sodium;   a second body of molten basic aluminate salt;   a ceramic separator which transports sodium ions between said bodies disposed between and separating said bodies;   an anode connected to the first body; and   a cathode immersed in the second body said cathode comprising nickel chloride containing a dispersion of a minor amount of particles of a transition metal having a lower potential than nickel.   
     
     
       8. A cell according to claim 7 in which the transition metal is present in the cathode in an amount from 1 to 25 percent by weight. 
     
     
       9. A cell according to claim 8 in which the transition metal reversibly chlorinates during charge-recharge cycling of the cell. 
     
     
       10. A cell according to claim 9 in which the transition metal is selected from the group consisting of cobalt, manganese and iron. 
     
     
       11. A cell according to claim 7 in which the second body includes from 0.1 to 5 percent by weight of sulfur. 
     
     
       12. A cell according to claim 11 in which the second body contains from 0.5 to 1.0 percent by weight of sulfur. 
     
     
       13. A cell according to claim 7 in which the cathode is formed from a sintered mixture of particles of nickel, the transitions metal and sodium chloride.